Question

1. Match the lumber column section to their appropriate size factor (Cf)

   -       A.       B.       C.       D.       E.       F.       G.    8x10 Eastern White Pine Select Structural       -       A.       B.       C.       D.       E.       F.       G.    4x6 Hem-Fir No 1       -       A.       B.       C.       D.       E.       F.       G.    2x4 Douglas Fir Larch No 2       -       A.       B.       C.       D.       E.       F.       G.    12x12 Northern Pine Select Structural       -       A.       B.       C.       D.       E.       F.       G.    4x4 Western Cedar No 1

   A. 1.15 B. 1.1 C. 1.0 D. 1.4 E. 1.3 F. 1.2 G. 1.05

5 points   

QUESTION 2

1. "A 12ft tall column is made of 4x8 Douglas-Fir-South #1 wood. If the column is pinned (hinged) at both ends, calculate the service load capacity, in whole pounds, of the column. Assume normal temperature and moisture conditions."

1 points   

QUESTION 3

1. "A 12ft tall column is made of 5x5 Hem-Fir #2 wood. If the column is pinned (hinged) at both ends, calculate the service load capacity, in whole pounds, of the column. Assume normal temperature and moisture conditions."

1 points   

QUESTION 4

1. "An 18ft tall column is made of 4X6 Douglas-Fir-South Sel Struct wood. If the column is braced half-way on its weak axis and its hinged on both ends, calculate the column service load capacity. Assume normal conditions."

1 points   

QUESTION 5

1. "An 18ft tall column is made of 6x8 Douglas-Fir-South #1 wood. If the column is braced half-way on its weak axis and its hinged on both ends, calculate the column service load capacity. Assume normal conditions."

Answer 1

Ans) We know,

  Eastern white pine select structural 8 x 10 has

C_f = 1.0 so correct match is C

4 x 6 hem-phir No 1 has

C_f = 1.05 so correct match is G

2 x 4 Douglas fir larch has

C_f = 1.15 so correct match is A

12 x 12 Northen pile select structural has

C_f = 1.0 so correct match is C

4 x 4 Western cedar no1 has

C_f = 1.15 so correct match is A

Ans 2) Given,

Length of column = 12 ft

Cross section of column = 4 x 8 Douglas fir (Nominal dimension 3.5 x 7.5)

Column capacity = F'c x C_p x Area ,where Cp is column stability factor

F'c = Fc x C_f x C_m x C_d

where, Fc = compressive strength  parallel to grain

C_f = size factor

C_m = wet service factor

C_d = Load duration factor

Fc for Douglas fir = 1100 psi

F'c = 1100 x 1.05 x 1 x 1

= 1155 psi

Cp = (1 + K)/2c - [ {(1+K)/2c}² - K/c]^0.5

where c = 0.85 and K = Fc/F^'c

On solving , C_p = 0.345

Capacity = 1155 x 0.345 x 3.5 x 7.5

= 10460 lb

Ans 3) Given,

5 x 5 Hem fir No 2 with Fc = 1300 psi

F'c = 1300 x 1.1 x 1 x 1

= 1430 psi

Cp = 0.298

Capacity = 1430 x 0.298 x 4.5 x 4.5   

= 8630 lb

Ans 4) Given,

4 x 6 Douglas fir with Fc = 1700 psi

F'c = 1700 x 1.1 x 1

= 1870 psi

Slenderness ratio in weak direction = (1 x 9 x 12) / 3.5

= 30.80

E'min = Emin x Cm x Ct

= 620000 x 1 x 1

Cp = 0.326

Capacity = 1870 x 0.326 x 3.5 x 5.5

= 11735 lb